1. Technical Field
The present invention relates to a chip antenna having main and auxiliary antenna elements juxtaposed to each other, and more particularly, to a chip antenna configured to reduce a variation in antenna performance and a method of manufacturing the same.
2. Related Art
An antenna having an antenna element of a plate-shaped or meander-shaped conductor embedded in or stacked on a dielectric chip is known. It is also known to provide an auxiliary passive antenna element juxtaposed with a main antenna element, to thereby broaden the bandwidth of an antenna or make an antenna having multi-resonance frequencies.
In the latter chip antenna, it is predicted that relative positions of the main and auxiliary antenna elements 1 and 2 are deviated from each other in the lateral or height direction as shown in FIG. 11 or 12 when the antenna elements 1, 2 are embedded in the dielectric chip 3. This applies to a case where the antenna elements 1, 2 are stacked on the dielectric chip 3.
Such a positional deviation between the antenna elements 1 and 2 varies the opposed or overlay area of the opposed end edge portions of the antenna elements, to cause a variation in capacitance (impedance) between the antenna elements 1 and 2, resulting in a change in antenna performance. As a consequence, it is predicted that difficulties will be encountered in manufacturing chip antennas which are uniform in antenna performance.
An object of the present invention is to provide a chip antenna having a main antenna element and an auxiliary passive antenna element that are juxtaposed to each other and being capable of easily and effectively suppressing a variation in antenna performance.
Another object of the invention is to provide a method of manufacturing a chip antenna which is provided with a main antenna element and an auxiliary passive antenna element and which is free from a variation in antenna performance.
According to one aspect of the present invention, there is provided a chip antenna which comprises a main antenna element and an auxiliary passive antenna element that are embedded into or stacked on a dielectric chip. The main antenna element has a first main body and first expanding portions individually extending outwardly from both ends of an inner end edge portion of the first main body in a width direction of the chip antenna. The auxiliary antenna element has a second main body and second expanding portions individually extending outwardly from both ends of an inner end edge portion of the second main body in the width direction of the chip antenna. The inner end edge portions of the main and auxiliary antenna elements, including the first and second expanding portions, respectively, are opposed to each other with a spacing therebetween in a lengthwise direction of the chip antenna.
According to the chip antenna of this invention, the inner or opposed end edge portions of the main and auxiliary antenna elements have the width size greater than that of the main body by the projecting length of the expanding portions. For instance, the width size is equal to or greater than the entire width of the dielectric chip. Thus, the inner end edge portions of the main and auxiliary antenna elements are opposed to each other over substantially the entire width of the dielectric chip, even if the antenna elements are subject to a positional deviation in the widthwise direction, so that the opposed area and hence the capacitance or impedance between the antenna elements may hardly change, whereby a variation in antenna performance is suppressed.
According to another aspect of the present invention, there is provided a method of manufacturing a chip antenna, which comprises: a first step of forming a conductor plate having a main antenna element that has a first main body and first expanding portions individually extending outwardly from both ends of an inner end side portion of the first main body, an auxiliary passive antenna element that has a second main body and second expanding portions individually extending outwardly from both ends of an inner end side portion of the second main body, and a coupling portion that couples the main and auxiliary antenna elements to each other, with the inner end edge portions of these antenna elements opposed to each other with a spacing therebetween in a lengthwise direction of the chip antenna; a second step of embedding or stacking the conductor plate into or on a dielectric chip; and a third step of cutting off the coupling portion of the conductor plate from the main and auxiliary antenna elements of the conductor plate embedded into or stacked on the dielectric chip, to thereby cut off the main and auxiliary antenna elements from each other.
With the chip antenna manufacturing method of this invention, a chip antenna having opposed end edge portions extending over at least the entire width of a dielectric chip can be easily and efficiently fabricated. That is, the antenna elements of a conductor plate formed in the first step are disposed in substantially the same plane, so that the opposed or inner end edge portions of the antenna elements are accurately opposed to each other with a predetermined spacing therebetween in the lengthwise direction. In the second step wherein the conductor plate is embedded into or stacked on the dielectric chip, the antenna elements are hardly subject to a positional deviation in any of the height, widthwise and lengthwise directions of the chip antenna since the antenna elements are kept coupled to each other by a coupling portion. Also in the third step, the main and auxiliary antenna elements are hardly subject to a positional deviation since the antenna elements formed in the conductor plate are cut off from each other by cutting off the coupling portion from the antenna elements in a state that the conductor plate is partly embedded into or stacked on the dielectric chip. As a consequence, a chip antenna, having the main and auxiliary antenna elements whose opposed or inner end edge portions are accurately opposed to each other and being free from a variation in antenna performance, can be easily and efficiently fabricated.